Apparatus for and method of measuring a peak jitter

Abstract

An input clock signal is transformed into a complex analytic signal z c (t) by an analytic signal transforming means 13 and an instantaneous phase of its real part x c (t) is estimated using the analytic signal z c (t). A linear phase is removed from the instantaneous phase to obtain a phase noise waveform Δφ(t). A peak value Δφ max of absolute values of the Δφ(t) is obtained, and 4Δφ max is defined as the worst value of period jitter of the input signal. The Δφ(t) is sampled at a timing close to a zero-crossing point of the x c (t) to extract the sample value. A differential between adjacent samples is obtained in the sequential order to calculate a root-mean-square value of the differentials (period jitters). An exp(−(2Δφ max ) 2 /(2σ j 2 )) is calculated from the mean-square value σ j and 2Δφ max , and the calculated value is defined as a probability that a period jitter exceeds 2Δφ max .

What is claimed is:  
     
       1. An apparatus for measuring a peak jitter comprising: 
       analytic signal transforming means for transforming an input signal into a complex analytic signal;  
       instantaneous phase estimating means for obtaining an instantaneous phase of the analytic signal;  
       linear phase removing means for removing a linear phase from the instantaneous phase to obtain a phase noise waveform;  
       peak detecting means for obtaining the maximum value of absolute values of the phase noise waveform as a peak value; and  
       worst value estimating means for obtaining the worst value of period jitter of the input signal from the peak value to output the worst value.  
     
     
       2. The apparatus for measuring a peak jitter according to  claim 1  wherein said worst value estimating means is means for multiplying the peak value by 2 to output the multiplied value as the worst value. 
     
     
       3. The apparatus for measuring a peak jitter according to  claim 1  wherein said worst value estimating means is means for multiplying the peak value by 4 to output the multiplied value as the worst value. 
     
     
       4. The apparatus for measuring a peak jitter according to  claim 1  further including: 
       zero-crossing sampling means for inputting thereto the phase noise waveform and for sampling the phase noise waveform at a timing close to a zero-crossing timing of a real part of the analytic signal to output a sample output; and  
       switching means for switching a signal path of the phase noise waveform from said linear phase removing means so that the sample output from said zero-crossing sampling means is supplied to said peak detecting means.  
     
     
       5. The apparatus for measuring a peak jitter according to  claim 1  further including: 
       clipping means for removing amplitude-modulation components from the input signal to supply the input signal from which the amplitude-modulation components have been removed to said analytic signal transforming means.  
     
     
       6. The apparatus for measuring a peak jitter according to  claim 2  further including: 
       mean-square value detecting means for inputting thereto the phase noise waveform to obtain a mean-square jitter of the period jitters; and  
       probability calculating means for inputting thereto the worst value and the mean-square jitter to obtain and output a probability that the period jitter exceeds the worst value.  
     
     
       7. The apparatus for measuring a peak jitter according to  claim 6  wherein said mean-square value detecting means comprises: 
       zero-crossing sampling means for sampling the phase noise waveform at a timing close to a zero-crossing timing of a real part of the analytic signal to extract a sample output;  
       differential means for calculating a differential waveform of the sampled phase noise waveform to obtain the period jitter; and  
       mean-square value detecting means for calculating a mean-square value of the period jitters to obtain the mean-square jitter.  
     
     
       8. A method of measuring a peak jitter comprising the steps of: 
       transforming an input signal into a complex analytic signal;  
       obtaining an instantaneous phase of the analytic signal;  
       removing a linear phase from the instantaneous phase to obtain a phase noise waveform;  
       obtaining the maximum value of absolute values of the phase noise waveform as a peak value; and  
       obtaining the worst value of period jitter of the input signal from the peak value.  
     
     
       9. The method of measuring a peak jitter according to  claim 8  wherein said step of obtaining the worst value is a step of multiplying the peak value by 2 to obtain the multiplied value as the worst value. 
     
     
       10. The method of measuring a peak jitter according to  claim 8  wherein said step of obtaining the worst value is a step of multiplying the peak value by 4 to obtain the multiplied value as the worst value. 
     
     
       11. The method of measuring a peak jitter according to  claim 8  further including the step of: 
       removing amplitude-modulation components from the input signal prior to transforming the input signal into the analytic signal.  
     
     
       12. The method of measuring a peak jitter according to  claim 9  further including the steps of: 
       obtaining a mean-square jitter of the period jitters from the phase noise waveform; and  
       calculating a probability that the period jitter exceeds the worst value from the worst value and the mean-square jitter.  
     
     
       13. The method of measuring a peak jitter according to  claim 12  said step of obtaining the mean-square jitter comprises the steps of: 
       sampling the phase noise waveform at a timing close to a zero-crossing timing of a real part of the analytic signal to extract a sample output; and  
       calculating a differential waveform of the phase noise waveform sampled in said sampling step to obtain the period jitter; and  
       calculating a mean-square value of the period jitters to obtain the mean-square jitter.